1. Field of the Invention
This invention relates generally to a multi-v-ribbed power transmission belt, more particularly to a v-ribbed belt having protruding fiber at a pulley-contacting surface, and specifically to a belt having protruding deformable fibers which stand erect or slightly bowed and which are deformed into an oval cross-sectional shape.
2. Description of the Prior Art
Power transmission belts such as v-belts, multi-v-ribbed belts and flat belts rely on friction between a contact surface and a pulley or sheave to transmit power from a driver sheave to the belt surface and thence to a driven sheave. A typical belt construction includes a tensile member, an elastomeric belt body having discontinuous synthetic thermoplastic and/or natural fibers embedded therein, and a pulley contact surface. A rubber contact surface may generate a high friction coefficient and may be associated with undesirable frictional noises. Exposure of the ends of the embedded fibers at the contact surface may reduce the friction coefficient or otherwise control friction and may alleviate some noise problems. Accordingly various configurations of exposed fibers have been tried.
Japanese Unexamined Patent Publication H04-348930 discloses a method of polishing the surface of a rubber structure having short thermoplastic fibers so as not to soften and melt the short fibers. The short fibers disclosed in that publication are illustrated by fibers 1a in FIG. 1 which do not appear to protrude more than about one fiber diameter. Disclosed as prior art in that publication are similar fibers with melted ends as illustrated by fibers 1b in FIG. 1.
Japanese Unexamined Patent Publication H05-8294 discloses as prior art nylon fiber ends that are round and have hardly come out from the surface as illustrated by fiber 1c in FIG. 1. Also disclosed in that publication is a rubber structure with meta-aramid staple fibers with a long extension from a surface and lots of curl as illustrated by fiber 1d in FIG. 1, resulting in increased fiber occupancy area and a surface with low coefficient of friction. Also disclosed in that publication is a rubber structure with para-aramid or cotton staple fibers with a short extension from a surface and split ends illustrated by fiber 1e in FIG. 1, resulting in a surface with high coefficient of friction.
U.S. Pat. No. 5,498,212 discloses a power transmission belt having embedded aramid fibers. The exposed ends of para-aramid fibers are fibrillated and tend to curl as illustrated by fiber 1f in FIG. 1.
U.S. Pat. No. 5,197,928 discloses a v-ribbed power transmission belt having embedded synthetic or natural fibers. The exposed surface of the belt fibers is flared by melting or other method so that its effective diameter is increased over the undeformed cross-sectional area of the body of the fibers as illustrated by fiber 1g in FIG. 1.
U.S. Pat. No. 5,413,538 discloses a v-ribbed power transmission belt having synthetic or natural fibers embedded in the belt body, no significant number of which project from the pulley-engaging surface, and embedded aramid fibers which do project from the same surface. If any non-aramid fibers project from the surface, it is characterized as stubble.
U.S. Pat. No. 5,904,630 discloses a machined, molded, ribbed, power transmission belt having embedded natural or synthetic fibers. Surplus material 0.1 to 0.3 mm thick is machined from the ribs so as to uncover protruding ends of the fibers. There is significant dispersion in directions of the fibers.
U.S. Pat. No. 6,435,997 discloses a v-ribbed belt having synthetic fibers protruding from a rib face. The extruded section of the fiber is plastically deformed in the shape of sectors gradually broadened toward their distal ends as illustrated by fiber 1h in FIG. 1. The fiber is kept unmelted and formed at its distal end in the shape of waves. The rib surface has microscopic unevenness with a level difference of 0.5 to 10 μm as illustrated by unevenness 1j in FIG. 1, and preferably with a wavy shape.
U.S. Pat. No. 6,695, 735 discloses a v-ribbed belt having short aramid fibers protruding from a rib face. The root portions of the extruded short fibers are raised form the face, and the tip portion is bowed in a different direction from its medial portion as illustrated by fibers 1i in FIG. 1. The bowing directions of fibers differ from one another to decentralize the orientation thereof.
U.S. Pat. No. 4,798,566 discloses a raw-edge power transmission belt having embedded discontinuous aramid fibers with protruding portions bent against the elastomeric body portion of the belt in such a manner as to expose lateral side portions of fiber which define part of the friction driving surface as illustrated by fibers 1k in FIG. 1. Most of the aramid fibers protrude from 0.1 to 0.3 mm.